A power source may be used to drive generators and machines. The power source may be, for example, an engine, such as a diesel engine, gasoline engine, natural gas engine, or any other source of mechanical or rotational energy. A generator converts mechanical power received from the engine into electrical power.
Examples of machines may include excavators, loaders, dozers, motor graders, haul trucks, and other types of heavy machinery used for a variety of tasks. The power source provides the power required to complete these tasks. For example, a machine may include an engine-driven pump that provides high pressure fluid to move actuators associated with an implement or traction devices of the machine. In another example, the machine may include a transmission that converts engine torque to drive traction devices, such as wheels or tracks that propel the machine.
Ideally, the engine drives the generator or machine with a relatively constant torque and speed. However, external changes in load on the generator or machine may be severe enough to affect engine operation and cause engine lugging. Engine lugging, or excessive engine speed droop, may decrease the productivity and efficiency of the engine.
For example, in the case of the generator, an external electrical load may suddenly be applied to the generator, which subsequently demands an increased power from the engine to provide the increase in electrical power demand. As a result of the sudden increased electrical load, the engine may lug, or decrease in speed as the torque load increases. Similarly, in the example of the engine-driven pump, an operator or particular operational situation of the machine may require an increased amount of power from the engine to drive the pump. If this increased amount in power demand exceeds an immediate output capacity of the engine, then the engine may experience lugging.
In the case of the machine transmission, when a sudden increase in torque is required at a faster output speed than an immediate capacity of the engine, then the engine may lug or engine speed may droop. With all these examples, as a result of engine lugging, the generator, pump, or transmission may produce undesirable fluctuations in output as a response to the sudden increase in load.
Operating techniques for a turbocharged internal combustion engine to better accommodate load changes are disclosed in U.S. Pat. No. 6,408,625, entitled, “Operating Techniques for Internal Combustion Engines.” The '625 patent describes preparing an engine to accept a generator load by increasing boost pressure provided by the compressor. More specifically, the boost pressure increase is accomplished in the '625 patent by skip-firing the cylinders in a selected pattern, retarding ignition timing for the cylinders, or a combination of these techniques. The '625 patent also describes a controller configured to generate a signal to indicate that the engine is ready to accept block loading from the generator.
However, the '625 controller only manages power on the engine side of a generator set. Accordingly, there is a need to provide a control system and method that manages power on the generator side to reduce engine lug, and which can be applied to both generators and machines.